الفهرس 
Statistical analysis proceduresOnly 14 pages are availabe for public view
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Abstract
The present investigation aimed to study the genetic behaviour of groups of white inbred lines through their single crosses over the two years (1 993+1994) in the farm of the Faculty of Agriculture, kafi El- Shew, Tanta University. The genotypes were tested in an experiment consisted of the 45 crosses plus four commercial hybrids i.e., (S.C. 10 - S.C. 122 - T.W.C. 310 - T.W.C. 320) as controls. The 49 genotypes were tested in a randomized complete block design, with four replicates. The variation among entries in each experiment were calculated in both years. The analysis of variance for both years (1993+1994) were combined in one analysis of variance including, between the genotypes [crosses, checks and crosses versus checks or superiority(s)], years and the possible interactions among them. Average heterosis were calculated relative to the general mean of all crosses. the variations among crosses were fiuther partitioned into the general and specific combining ability, components. Also, general and specific combining ability effects for the ten inbred lines were computed according to Griffing’s method 4 model-I (1 956). The data were measured on grain yield kg/plot (adjusted to arad./fad.), sikng date, plant and ear height (cm), number of eadplant, ear length (cm), ear diameter (cm), number of rows/ear, number of kernels/row and weight of 100 kernels (grn): RrnT : Grain yield: The results obtained fiom th~s character could be summarized as follows: 1- Grain yield was affected by years however, 1994 season produced the hghest yields than 1993 season for the crosses and controls, it means that the environmental conditions of 1994 season was more suitable for yielding productivity than that of 1993 season. 2- Heterosis in percent for each cross relative to the general mean of all crosses was computed and out of the 45 crosses, the cross 9x1 0 (Katta- 14 x Katta- 1 5) indicated the highest heterosis percentage of 126.34%. Also the cross 3 x 10 (Katta-4 x Katta-15) indicated the lowest heterosis percentage of 76.38% 3- As an average over the two years (1 993 + 1994) the means of the crosses varied fiorn 3.3 12 kg./plot or 23.66 arad./fad. for the cross (3 x 10) to 5.478 kg./plot or 39.13 arad./fad. for the cross (9x 10) with an average of 4.36 kg./plot or 30.97 arad./fad. 4- The mean square of general and specific combining ability in case of absolute values are highly significant. However, the interaction with years were highly significant, indicating that g.c.a. (or additive effects) and s.c.a. (or non-additive effects) are important in this trait In addition the main effects of g.c.a. is more important than that of s.c.a., while, the reverse was obtained for either the interaction of them with years 5- The data indicated that only five crosses i.e. 9x10 (Katta-14 x Katta 15), 4 x 10 (Katta-6 x Katta-15) ,6 x 9 (Katta-9 x Katta-14) , I x 4 (Katta-2 x Katta-6) and 5 x 9 (Katta-7 x Katta-14) out of 45 crosses produced higher mean yield than the mean of the hghest ylelder check S.C. 10, however, there was no sigmficant dzfferences among each mean of these crosses and the mean of that check, while the cross 9 x 10 (Katta-14 x Katta-15) significantly outylelded the mean of each of the other three checks (s.c. 122, T.W.C. 3 10 and T.W.C. 320). The number of the crosses which each of them did not differ significantly fiom the mean of each of those three checks mentioned above where 16, 20 and 19 as well as the cross (9x10), respectively. Also, the data indicated that the lines number 9 and 10 were common sharing hes in the four groups of the checks followed by lines number 5 and 6 for the grain yield. 6- It could be concluded fiom the previous results that the inbreds with hgh yielding ability and superior genetic behaviour in crosses through this study, could be considered promising materials which may be used immediately for improving maize breeding programes in Egypt. 7- The results indicated that the high yielding ability for the crosses may be due to the high g.c.a. and s.c.a. of the parents involved of those crosses.